For a history paper, my argument is that the American Frontier acted as a sort of pressure relief valve for Colonial dissidents who did not agree with Puritan theology. What is a more appropriate word or term for pressure relief valve?

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

But what they call The Great Migration was Puritans heading for the new land because they weren't happy with their circumstances and treatment in England.
–
FumbleFingersNov 24 '12 at 1:23

@FumbleFingers: I think the O.P. is referring to an exodus of folks from those original colonies to what we call the "Old West" or "Wild West", beginning in the early 1800s.
–
J.R.Nov 24 '12 at 1:26

No close votes needed I think. Frankly, I see a good question here, but fail to find the right answer to offer. Should come back if I find any luck.
–
KrisNov 24 '12 at 8:25

1

Voting to close because I have no idea what you mean by "more appropriate" term. There's nothing obviously wrong with just saying "release valve" so without knowing what you find distasteful about it, it's hard to offer any alternatives.
–
LynnNov 26 '12 at 2:31